Tercio

A tercio was a Spanish infantry unit and formation consisting of up to 3,000 troops, divided into between ten and twelve companies of pikemen, swordsmen, and arquebusiers/musketeers. The tercios were known for pioneering the pike square, which delivered them several victories during the Italian Wars. The formation was used by the Habsburg domains of Spain and the Holy Roman Empire, and they dominated European battlefields in the sixteenth century and the first half of the seventeenth century. The defeat at the 1643 Battle of Rocroi led to the decline of the tercio as infantrymen came to depend more on firearms than melee weapons.